JPS6171477A - Recording disc information reproducing device - Google Patents

Abstract

PURPOSE:To attain PCM demodulation without jitter by setting the cut-off frequency of a loop filter inserted in the loop of a PLL circuit for generating read clock lower than the warp frequency of a recording disc at reproduction so as to eliminate jitter component due to the eccentricity of the disc. CONSTITUTION:Since the mechanical system such as an actuator drive device cannot sufficiently track the high frequency component of residual jitter even in a tangential servo system, jitter cannot completely by eliminated. Then in the digital information demodulation system 14, the cut-off frequency of the LPF 32 of a PLL circuit generating a read clock is set lower than the maximum frequency of the band of a tangential servo loop to cut the high frequency component of the residual jitter thereby eliminating the residual jitter component. More preferably, the cut-off frequency of the LPF 32 is set lower than the warp frequency of the disc (30-8Hz in LDD) so as to eliminate completely even the jitter due to the eccentricity of the disc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording disc information reproducing apparatus, and particularly to an I! I do it.

Technology For recording discs on which digital signals are recorded, audio signals are subjected to predetermined digital modulation processing]'I! A so-called compact disc (hereinafter referred to as CD), which is a digital audio disc recorded in the form of a pulse train, is known. A method in which a pulse train signal is digitized and recorded using a method (patent application 1984-457).
Video disc (hereinafter referred to as L D
(abbreviated as D) is being emitted [7i1.

In this recording method, the audio signal is converted into two channels, 2.3 MHz and 2.8 MHz.
audio carriers are each FM modulated by two audio channel signals. The video signal is frequency-converted so that the sync tip is 7°6 MHz, the pedestal level is 8.1 MHz, and the white beak is 9.3 MHz. Then, the audio signal is further converted into PCM (Pulse Code Modulus).
The signal is digitized and converted into a pulse train signal using a modulation method such as ration>.

This pulse train signal is, for example, an EFM (Eight to
The signal is suitable for recording using the Fourteen MOdLIlatiOn'') method, and the frequency spectrum is the frequency component of a pulse train with a width of 3T to 11T. Here, T indicates the bit period of the PCM signal, and the The pulse is approximately 720KHz, with a maximum width of 1
The 1T pulse has a frequency of about 200KHz. Such a pulse train signal is about 1/1 of the video main carrier.
The recording signal is superimposed at a level below 0, slice-amplified near the zero-crossing point, and becomes a pulse-width modulated signal, and the recording signal is interrupted.

RF (high frequency) is transmitted from a recording disk on which video signals and audio signals are recorded using the above recording method.
The frequency spectrum of the signal is as shown in FIG. In Fig. 1, the component indicated by A is a digitized audio signal component, the component indicated by B is an audio FM signal component, the component indicated by C is a color information component in a video FM signal, and the component indicated by D is a video FM signal. This is the embryonicity information component in 6.

Since the dynamic range of the digitized audio signal can be approximately 90 dB or more, the sound quality can be significantly improved compared to recording and reproducing audio signals using the FM modulation method.

By the way, in a general demodulating device for a PCM digital signal in a CD playback device, the bladder release clock is fixed,
On the other hand, by synchronizing the rotation of the recording disk in phase and reading out the information written to the -H memory using the loading clock synchronized with the reproduction clock signal in synchronization with the RAA output clock, jitter, which is a time axis fluctuation component, can be eliminated. Remove(&
It has become a reality.

On the other hand, when demodulating the digital signal extracted from the playback signal by the video playback device when playing the LDD, the playback signal is already synchronized with the reference signal for video synchronization, and the demodulation device in the conventional CD playback device When data is read from memory using a separate i11% signal on the PCM demodulation side, the reproduced video signal and the reproduced demodulated audio signal will be shifted in time due to the slight phase shift between the two reference signals. Otherwise, a blank space 2 may occur due to memory overflow or excessive reading of data.

Therefore, when developing a playback device that can play both CDs and LDDs, it is necessary to solve the various problems mentioned above when considering sharing the 1!2 tone system for the purpose of reducing costs. There is a need to.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and it is possible to reliably suppress the thick components included in the reproduced digital signal υ1 and generate a jitter-free digital signal whether reproducing a CD or reproducing an LDD. The purpose is to provide a recording disc information reproducing device that can reproduce 1q of signals! A recording disk information reproducing apparatus according to the present invention includes a demodulating means for demodulating a re-binized digital signal, and a demodulating means for outputting the demodulated output of the demodulating means to and from a memory in synchronization with a reproduced clock signal included in the reproduced digital signal. and a read clock generation circuit that generates a successive clock signal for reading two-bit information from the memory in synchronization with the reproduced clock signal,
A loop filter for the band vLti+I is inserted in the Il loop, and ath indicates that the cutoff frequency of the loop filter is set lower than the eccentric frequency of the previous two recording disks during reproduction.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing an embodiment of the recording disk information σ■ generating device according to the present invention. Such reproduction Kyoka is C
This is a so-called compatible player that can play back ordinary video discs (hereinafter referred to as LD) on which video signals and audio signals are frequency-modulated and recorded, as well as D and LDD. This player has a spindle motor 1 for driving the rotation of the LD and LDD, and a spindle motor 1 for driving the rotation of the LD and LDD, since the playback speed is different between the video disc (LD, LDD) and the digital audio disc (CD, ) as mentioned above. A p-drive spindle motor 2 is provided. These spindle motors 1.2 are selected depending on the type of disc to be reproduced, and for example, switching to use the motor 3 as the B drive source is switched by the horizontal 4.

In order to detect the disc size of the disc 5 to be reproduced, for example, three detection sensors 6, 7 and 8 are provided corresponding to the disc size in the disc radial direction. The disc size for CDs is approximately 5 inches in outer diameter <1
2co+), and in the case of video discs (LD, LDD), there are two types of outer diameter: 8 inches and 12 inches.The 6th output of the detection sensor 6.7 and 8 of the 3fi?! has a waveform of 4115 After the waveform is shaped by the circuit 9, it is supplied to the disk discrimination circuit 10.For example, as a detection sensor, tf
Optical '9 sensors are used, but are not limited to this.

The disc discrimination circuit 10 determines whether the disc to be played is a CD or an LDD based on the detection outputs of the detection sensors 6.7 and 8.
It is determined which of the three types of disks, LD and LD. A concrete circuit configuration of this disk discrimination circuit 10 is shown in FIG. In this diagram, in the case of CD,
The disk size is determined to be the minimum (120+11), and the detection output of the innermost detection sensor 6 and the inverter 79
．． The output of the AND gate circuit 78 which converts the inverted output of the detection sensor 7.8 which has passed through the detection sensor 80 into three-man power becomes the CD discrimination information.

That is, the detection sensor 6 is on, and the other detection sensors 7.
8 is off, it is determined to be a CD. In the case of a video disc, since the disc sizes are 8 inches and 12 inches, the detection output of the detection sensor 7 or 8 passes through the OR gate circuit 69 and becomes the output of each of the AND gate circuits 70 and 71. In addition, a frame synchronization detection circuit 2 to be described later
A frame synchronization detection signal generated when a frame synchronization signal is detected from 1 becomes another input to the AND gate circuit 71, and is also inverted by an inverter 72 and becomes another input to the AND gate circuit 70. and detection sensor 7 or 8
When a detection output is generated and a frame synchronization detection signal is input, LDD discrimination information is output from the AND gate circuit 71, and when the frame synchronization detection signal is not input, LD discrimination information is output from the AND gate circuit 7o. . This discrimination information is used to drive an indicator 11 that displays the type of disc, and as a switching signal for various switches to be described later.

A pickup 12 for reading recorded information from the disk 5 is supported by a slider base (not shown) that is movable in the radial direction of the disk 5.
The slider base is driven by a drive 8t (not shown) consisting of a slider motor, a G-speed gear, etc. Read information read from the recording disk 5 by the pickup 12 is supplied to a digital information demodulation system 14, an analog audio demodulation system 15, and a video 7 demodulation system 16 via an RF amplifier 13, respectively. The RF amplifier 13 has a wide X band of about 5 KHz to 14 MHz, and a single amplifier can amplify a reproduced PCM audio signal, a reproduced FM audio signal, and a reproduced video signal.

The digital mirror adjustment system 14 is mainly provided with a changeover switch 17 that changes depending on the type of disc to be played back. In case a
In the case of a CD, it switches to the i;tB side. In other words, the signal processing system for the reproduced digital signal can be switched between when playing an LDD and when playing a CD. When playing a CD, the reproduced RF output is PCM audio information, and this PCM audio information is compensated for by the equalizer 18, especially in the 8th range of frequency characteristics.
tionTransfer Function)
Complementary tO is applied.

On the other hand, in the case of LDD, FM audio information and FM
PCM audio information included in the reproduced RF signal together with the video information is extracted by an LPF (low pass filter) 19 and supplied to a de-emphasis circuit 20. PCM
Audio information is, for example, an EFM signal, but if the digital signal is directly converted into an FM-modulated video signal during recording, the digital signal component will be interfered with by the low-frequency component of the FM video signal. , the low frequency components are boosted and recorded. Therefore, during reproduction, the de-emphasis circuit 20 compensates for the low-frequency components boosted during recording without dropping them. This makes it possible to improve the S/N ratio of the digital signal with respect to low frequency noise during recording and reproduction.

Note that instead of switching the signal processing system using the changeover switch 17, the power supply to each signal processing system circuit is set to 0N.
A similar effect can be obtained by using 10FF.

The reproduced EFM signal that has passed through the changeover switch 17 is supplied to the EFM demodulation circuit 22 via the frame synchronization detection circuit 21 and is also supplied to the reproduced clock extraction circuit 23. The EFM demodulation circuit 22 demodulates the signal into a PCM digital signal.

This demodulated signal is written into a memory 24 such as a RAM (random access memory) under the control of a memory controller 25. At this time, the memory controller 25 uses the same frequency as the write clock, which is the frequency-divided output from the frequency divider 26 of the reproduced clock. 9J and write.

Reading of stored information from the memory 24 is performed in synchronization with a read clock obtained by dividing the oscillation output of a vCO (voltage controlled oscillator) 27 in a PLL (phase locked loop) circuit by a frequency divider 28. It has become so. The PLL outlet is the aforementioned vCO27
, the divided output of the reproduced clock by the frequency divider 29 and vCO2
A phase comparator (P/C) 31 which uses the divided output of the oscillation output of 7 and the frequency divided output by the frequency divider 27, an LPF (0=pass filter) 32 which receives this comparison output as input, and this LPF.
32 and a change-over switch 33 that selectively supplies the output voltage of 32 and the base Q-lightning voltage rer+ to the vCO 27.

In this PLL circuit, the change-over switch 33 is set to the a side during LDD playback and switches the output voltage of the LPF 32 to the b side during CD playback, based on the discrimination result of the disc discriminating circuit 10 mentioned above, and switches to the b side during CD playback. pressure Vref,
is supplied to vCO27. As a result, during LDD playback, the output clock for reading stored information from the memory 24 is synchronized in phase with the playback clock by the P L 1 circuit, and during CD playback, the loop switch 59, which will be described later, is turned on (opened). Phase comparator 31
By driving the CD rotation drive spindle motor 2 through the LPF 77, the reproduced clock is phase-synchronized with the fixed clock obtained by the vCO 27 whose bias is in a fixed state.

The digital signal thus read out is converted into an analog audio signal by a D/A (digital/analog) converter 34, and then sent to an LPF 35L.

Left and right playback audio outputs are provided via 35R.

The usage status in the memory 24 is constantly monitored by the memory controller 25, and when the memory 24 overflows or becomes blank (no data), the controller 25 sends information indicating these statuses to the voltage generator 3.
Supply to 6. During LDD regeneration, this voltage generator 36
generates a positive control voltage when the memory 24 overflows, and generates a negative v1 voltage when the memory 24 becomes blank, according to information indicating the usage status of the memory 24 from the memory controller 25. , superimposed on the output voltage of the LPF 32 and supplied to the vCO 27 via the changeover switch 33
In particular, the frequency of the starting point 0 is set to υ1.

In this way, m8 of the data stored in the memory 24 is monitored from time to time, and when there is an excess or deficiency in the capacity ω and processing capacity of the memory 24, a positive or n v1υu voltage is generated to cause the PLL circuit to take action. By making this request, the memory 24 can always be maintained in a normal state.

In the analog audio demodulation system 15, the reproduction RF (H
The output of the BPF (band pass filter > 371, 37R, which passes only the audio carrier components of 2.3 MHz and 2.8 MHz from the signal,
38RIC#rFMtu tune h, and becomes left and right playback audio outputs via de-emphasis circuits 39L and 39R.

In the video demodulation system 16, only video information is extracted from the reproduced RF signal by a BPF & notch circuit 40. , this B
In the PF & notch circuit 40, the EFM components included in the reproduced RF signal and 2.3MHz, 2.8M
Hz audio carrier components are actively removed. This extracted information is supplied to the FM demodulator 42 via the limiter circuit 41 and is FM demodulated. This demodulated output is passed through a dropout compensator (DQ
C) 44 and dropout at 6 to the compensator 44? l1irri is done. This dropout MtB device 44 includes, for example, a dropout sensor (DO8
) 46 detection output, and the analog switch that is turned off by the detection output of 46, and the base t%! and a hold capacitor provided between the potential point and the potential point. Therefore, when a dropout occurs, the level of the output of the LPF 43 immediately before the output of the dropout sensor 46 is held and sent to the next stage circuit, thereby performing dropout compensation. The output of this dropout compensator 44 becomes a video output.

The output of the dropout compensator 44 is sent to the horizontal sync separation circuit 4.
7, and the horizontal synchronizing signal is separated and output. This horizontal synchronizing signal is supplied to phase comparators 48 and 49, and the phase difference with the reference signal output from the reference signal generator 50 is detected. The output of the phase comparator 48 serves as an input to the adder 51, and the output of the phase comparator 49 supplies the equalizer amplifier 5.
It serves as another input to the adder 51 via 2. The output of the adder 51 is the equalizer amplifier 53 and the driver 5.
4, the LD[) and the spindle motor 1 for driving the LD rotation are driven. This is the spindle servo system. Further, the output of the equalizer amplifier 52 is connected to a loop switch 55,
An actuator (not shown) built into the pickup 12 is driven via the changeover switch 56 and the driver 57.

By driving this actuator (E), a light spot for reading information is arranged in the tangential direction of the recording track of the disk. This is a tangential servo system. The actuator may be a tangential cell mirror that rotates to bias the information reading light spot in the tangential direction of the recording track of the disk, or it may bias the lens in the direction perpendicular to the optical axis. It is also possible to have a configuration in which the light spot for reading the information ffi is moved in the tangential direction of the recording track of the disk by displacing the light spot.

The loop switch 55 is turned on (fi
ill formation) state. However, at the start of regeneration, the output of the phase comparator 48 first causes the spindle motor 1 to
is driven to control the time axis: j1 adjustment (spindle servo)
When the spindle servo is almost completely locked, the loop switch 55 is turned on and the actuator is driven by the output of the phase comparator 49 to perform fine adjustment of the time axis (tangential servo). . According to this, residual jitter components that cannot be removed by the spindle servo system can be removed by the tangential servo system.

However, even in the Kunstual servo system, the high frequency component of residual jitter is affected by the actuator drive mechanism'
Jitter cannot be completely removed because mechanical systems such as Jitter cannot follow it sufficiently. Therefore, in the digital information demodulation system 14 mentioned above, the P
By setting the cutoff frequency of the LPF 32 of the LL circuit lower than the maximum frequency of the band of the tangential servo, cutting the high frequency components of residual jitter,
This means that residual jitter components can be removed. More preferably, by setting the cutoff frequency of the LPF 32 lower than the disk eccentricity frequency (30 to 8H2 in the case of LDD), it is possible to completely eliminate jitter caused by disk eccentricity.

Although the spindle servo and tangential servo are performed based on the horizontal synchronization signal, similar effects can be obtained by performing the spindle servo and tangential servo based on the 3.58 MH2 color DI carrier wave included in the reproduced FM video signal.

The above is a servo system when reproducing a video disc (LDD, LD), but when reproducing a CD, spindle servo is performed based on the output of the phase comparator 3°1 in the digital information demodulation system 14 mentioned above. That is, the output of the phase comparator 31 drives the spindle motor 2 for driving the CD rotation via the loop switch 59 and the driver 60, which are turned on (closed) during CD reproduction. Conventionally, when playing a CD, the single tangent servo mentioned above was not performed, but the spindle motor 2 was
8 of the output signal of the phase comparator 31 which is the axis error signal between
In this example, H
The high-frequency component of the time axis error signal taken out by the PF 61 drives the Akuboo'ator in the pickup 12 via the changeover switch 56 and driver 57 (Novo, i.e., tangential servo is also adopted. The selector switch 56 is switched to the a side when playing a DD or LD, and to the b side when playing a CD, based on the discrimination result of the disc discrimination circuit 10.

Although the tangential servo during CD playback is performed based on the divided output of the reproduced clock extracted by the reproduced clock extraction circuit 23, Even if it is performed based on the frequency output, the same effect can be obtained since the frame synchronization signal and the reproduced clock are in a synchronous relationship.

The output of the spindle lock detection circuit 58 is connected to the inverter 62.
This signal is inverted and becomes the sole power of the OR gate circuit 63 as a spindle unlock signal indicating that the spindle servo system is not in the locked state.

As another input to the OR gate circuit 63, a random access information signal generated at the time of a random access command such as scan, search, jump, etc. is supplied. Furthermore, the LDD information output from the disk discrimination circuit 10 is also input to the OR gate circuit 63.

The output of the OR gate circuit 63 is supplied to the recovered clock extraction circuit 23 via the ultimate command circuit 64.

A concrete circuit configuration of the recovered clock extraction circuit 23 is shown in FIG. In this figure, the reproduced EFM signal is transmitted to the phase comparator 6.
5, the phase difference with the oscillation output of VCO<snow pressureゐ1ltiI1 oscillator) 66 is detected, and the phase difference signal is
It is supplied to the VCO 66 via F67 and a changeover switch 68. With the above, the PLLD that generates the recovered clock
The road is constructed.

Normally, the changeover switch 68 is always set to the a side to supply the output of the LPF 67 to the VCO 66, but when a command signal is output from the control command circuit 64 mentioned above, it is switched to the b side in response to this command signal. The predetermined reference voltage Vref2
is supplied to the VCO 66.

However, when the spindle servo is not in a locked state or when the information reading optical spot jumps tracks due to a random access command such as a scan, search, or jump, the reference voltage Vref2 is applied to the VCO 66 to change its oscillation frequency. By fixing the frequency to a value close to the reproduced clock frequency, the output of the reproduced clock can be accelerated after the spindle servo is locked or the random access command is released.

Referring again to FIG. 2, the audio output section includes a pair of left and right output terminals 73L and 73R of the analog audio output system.
A pair of left and right nine output elements 74L and 74R of a digital audio output system are provided. Output terminal 73L
, 73R are supplied with the audio output from the analog audio recovery system A 14. This audio output is LD
During playback, the output terminal 74L,
Also supplied to 74R. The selector switch 75 is in the normal state when the LD is being played, and is in the a gllll position.
D.

When playing a CD, the switch is switched to the b side based on the disc discrimination information from the disc discrimination circuit 1C11 and the like. The audio output from the digital information demodulation system 14 is controlled by left and right mode changeover switches 76L, 76R and changeover switches 75L, 7.
It is supplied to outputs 9a 74L and 74R via 5R.

As a result, during playback, the output terminal 73 is output.

Normal audio signals are output from the output terminals 73R and 74L and 74R, and when playing an LDD or CD, high-quality audio signals are output from the output terminals 74L and 74R, and when playing an LODCD, a high quality audio signal is output from the output terminals 73L and 73R. Also, normal audio words will be output.

The mode changeover switches 76L and 76R4 are provided to change over the output mode of digital audio audio signals in an analog stage. In other words, if the audio output from the digital audio demodulation system 14 is stereophonic, the above-mentioned output mode will suffice, but in the case of audio multiplexing, for example, the left channel will be Japanese and the R (right) channel will be foreign. mode changeover switches 76 that operate independently of each other;
By L and 76R, the audio output from the output terminals 74L and 74R can be switched to three output modes: Japanese and foreign languages, Japanese only, and foreign languages only. The driving of the mode changeover switches 76L and 76R is as follows.
These operations are performed separately according to control information from an operation unit (not shown).

Relays that operate independently are used as the mode changeover switches 76L and 76R. Normally, a relay with one movable contact and two fixed contacts is sufficient for signal switching, but in this example, a relay with an extra 1g movable contact and two extra fixed contacts is used. It is used. In other words, if we take the relay 761 on the L channel side as an example, there are two sets of movable contacts S that interlock with each other.
ll.

S21, and these two sets of movable contacts SI1. 211 fixed contacts Sν, +3, provided one pair for each S21;
The two fixed contacts 512 and 523 that are the most distant among the two sets of fixed contacts serve as input ends for the two signals (left and right audio signals), and one movable contact S
n is the output end. According to this, since two gaps exist between the left and right signal lines, crosstalk between the left and right signals can be reliably prevented. Of course, crosstalk can be more reliably prevented by increasing the number of contacts and providing more gaps.

Although not shown in the figure, a focus servo system that controls the position of the pickup 12 relative to the disk 5 in the direction perpendicular to the disk surface, and a tracking servo system that controls the position of the pickup 12 in the disk radial direction are also naturally provided. Therefore, even in these servo systems, it is preferable to switch the signal processing system for error signals between when playing a video disc (LDD, LD) and when playing a digital audio disc (CD), and the type of disc to be played. Despite this, it is possible to perform good servo.

In addition, the digital signal recorded on CD or LDD is
In addition to audio information, it also includes digitized comparison information, control information for the computer, and the like.

As explained above, according to the recording disc information reproducing apparatus according to the present invention, a loop fill is inserted into the loop of the read clock generation PLL circuit.

Since the cutoff frequency of the LPF 32 is set lower than the eccentricity frequency of the recording disk during playback, it is possible to remove jitter components caused by the eccentricity of the disk.
Since the jitter component contained in the reproduced digital signal is reliably suppressed and a read clock whose phase is used for the reproduced digital signal can be obtained, jitter-free PCM demodulation can be performed.

[Brief explanation of drawings]

Figure 1 shows the frequency spectrum of an RF signal obtained from a recording disk recorded by m-squares of a video signal and an audio signal subjected to frequency modulation processing, and a signal obtained by PCM modulating an analog signal and making it into a pulse. 2 is a block diagram showing a practical example of a recording disc information reproducing apparatus according to the present invention, and FIG. 3 is a block diagram showing a specific circuit configuration of a disc discrimination circuit in FIG. , FIG. 4 is a block diagram showing a specific circuit configuration of the recovered clock extraction circuit in FIG. 2. Explanation of symbols of main parts 1...Swiss spindle motor 2 for LD and LDD
...CD spindle motor 5...Recording disc 10...Disc discrimination circuit 12...Pickup 14...Digital information demodulation system 15...・・・
・Analog audio demodulation system 16...Video demodulation system

Claims (1)

[Claims] A recording disc information reproducing device capable of reproducing a recording disc on which a video signal and an audio signal are recorded by superimposing a frequency-modulated signal and a predetermined digital signal, the demodulating means demodulating the reproduced digital signal;
writing means for writing the demodulated output of the demodulating means into a memory in synchronization with a reproduced clock signal included in the reproduced digital signal; and generating a read clock signal for reading stored information from the memory in synchronization with the reproduced clock signal. A read clock generation circuit is provided, and a loop filter for band limiting is inserted in the control loop of the read clock generation circuit, and the cutoff frequency of the loop filter is lower than the eccentric frequency of the recording disk during reproduction. A recording disc information reproducing device characterized by a low setting.